Senate majority leader Harry Reid (D) of Nevada (c.) talks about political roadblocks to passing the highway bill during a news conference on Capitol Hill in Washington last week. The Senate passed its version of the bill Wednesday.

The Senate, after months of debate, passed a $109 billion, two-year bill funding the nation's transportation infrastructure in a lopsided vote on Wednesday.

The bill, which passed 74 to 22, marked a rare bipartisan triumph in the Senate. Now, the House must pass the Senate bill or its own version – a process that is complicated by divisions within Republican ranks.

Until the Senate and House agree, American businesses that rely on federal transportation dollars aren’t exactly stalled, but they can’t kick things into high gear, either.

“The highway system is our assembly line, and the only way we can have our assembly line improved is through the action of government,” said Randy Mullett, a spokesman for Con-Way, a $5.3 billion trucking and freight company headquartered in Ann Arbor, Mich. “Can you imagine any other business in the country that runs like that?”

Since the last long-term transportation funding bill expired in 2009, Congress has passed more than a half-dozen short-term funding extensions of a bill that once rocketed through both chambers, fueled by pork-barrel spending and the knowledge that every congressional district in America had potholes to fill.

At least two major hurdles remain before this bill can become law.

First, members of Congress might have to pass a temporary stopgap extension of transportation funding, because the current authorization runs out at the end of March. House Republicans, who return from work in their home districts next week, might not be able to settle on how to respond to the Senate proposal before then.

Then, the House will have to pass an actual transportation bill. House Speaker John Boehner (R) of Ohio has said he will take up the Senate bill “or something like it” this month, unless Republicans can come to terms on their own version. Rifts in GOP ranks have scuttled two other bills – one a five-year plan and the other an 18-month offering.

These delays leave some businesses champing at the bit because the summer construction season is coming, and every day spent wondering about future funding is one that delays a shovel going into the ground.

Ken Anderson, the president of the Marshalltown, Iowa (population: 27,552), Chamber of Commerce sees a trickle-down effect in local projects. Funding is a “constant unknown that’s out there as we deal with our state [department of transportation] or our local streets and roads people, and it seems like they can’t make decisions about projects going forward,” Mr. Anderson says. "Or one if they make a decision then the funding falls apart and then it's delayed and we're chasing our tails."

For the largest transportation projects, even a two-year bill doesn’t give much clarity on things to come, considering that completion times can be a decade or longer.

“Ideally we’d have a longer bill,” said Janet Kavinoky, executive director for transportation and infrastructure at the US Chamber of Commerce. “Because capital projects take a long time to plan and execute and for state and local [governments] who receive these funds, they need as much time horizon as they can to do major capital planning.”

This has knock-on effects. When governments waffle on projects, equipment manufacturers and distributors have a tough time convincing customers to make investments in their machinery. Workers, too, have good reason to want Congress to hit the gas: The long-suffering construction industry stands at 17 percent unemployment.

Should the bill pass as something similar to the current Senate version, it will have a number of improvements that will boost business, say many policy observers.

The bill consolidates federal transportation programs from roughly 100 down to a third as many.

It speeds up the delivery of projects by cutting back on regulations.

It offers more flexibility to states to partner with the private sector on infrastructure projects like privately funded roads.

Once famous for being stuffed with funds for members’ pet projects, the bill’s lack of earmarks and more efficient regulatory processes “will stretch every dollar farther,” said Ms. Kavinoky. “You don’t have to worry about the ‘bridge to nowhere’ problem.”

Yet that same legislative pork once greased the congressional skids for a bill that was a sure-fire winner in Washington.

“This used to be the easiest bill to pass on Capitol Hill,” Sen. Richard Durbin (D) of Illinois told reporters last week. “That’s why the House Public Works Committee [now known as Transportation and Infrastructure] has so many members – people couldn’t wait to get on that committee to pass this bill every five years.”

Amid today’s gridlock, however, it's perhaps pressure of the down-to-the-last-second variety that has replaced pork as the ultimate political lubricant.“We also do best when our backs are against the wall in Washington,” Mr. Mullett of Con-Way said. “The backs are kind of against the wall here.”